Publications (67) View all
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Article: Sequential Problems in Decentralized Detection With Communication
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ABSTRACT: Sequential problems in decentralized detection are considered. Peripheral sensors make repeated noisy observations of a binary hypothesis. At each time, a peripheral sensor has to decide whether to stop and send a final binary message to a coordinating sensor/fusion center or to continue taking costly measurements. The coordinating sensor's operation is explored under two different scenarios. In the first scenario, the coordinating sensor waits to receive the final message from each of the peripheral sensors and then starts taking costly measurements of its own. The coordinating sensor is then faced with a stopping problem on whether to stop and declare a decision on the hypothesis or to continue taking measurements. In the second scenario, the coordinating sensor starts taking measurements from the beginning, without waiting for the final messages from the peripheral sensors. At any time, the coordinating sensor has to decide whether to stop and declare a decision on the hypothesis or to continue to take more measurements and wait for the peripheral sensors to send their final message. Parametric characterization of optimal policies for the peripheral and the coordinating sensors are obtained under both scenarios. A sequential methodology for finding the optimal policies is presented.IEEE Transactions on Information Theory 09/2011; · 3.01 Impact Factor -
Article: Optimal Control Strategies in Delayed Sharing Information Structures
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ABSTRACT: The n -step delayed sharing information structure is investigated. This information structure comprises of K controllers that share their information with a delay of n time steps. This information structure is a link between the classical information structure, where information is shared perfectly between the controllers, and a non-classical information structure, where there is no “lateral” sharing of information among the controllers. Structural results for optimal control strategies for systems with such information structures are presented. A sequential methodology for finding the optimal strategies is also derived. The solution approach provides an insight for identifying structural results and sequential decomposition for general decentralized stochastic control problems.IEEE Transactions on Automatic Control 08/2011; · 2.11 Impact Factor -
Article: A Wireless Soil Moisture Smart Sensor Web Using Physics-Based Optimal Control: Concept and Initial Demonstrations
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ABSTRACT: This paper introduces a new concept for a smart wireless sensor web technology for optimal measurements of surface-to-depth profiles of soil moisture using in-situ sensors. The objective of the technology, supported by the NASA Earth Science Technology Office Advanced Information Systems Technology program, is to enable a guided and adaptive sampling strategy for the in-situ sensor network to meet the measurement validation objectives of spaceborne soil moisture sensors. A potential application for this technology is the validation of products from the Soil Moisture Active/Passive (SMAP) mission. Spatially, the total variability in soil-moisture fields comes from variability in processes on various scales. Temporally, variability is caused by external forcings, landscape heterogeneity, and antecedent conditions. Installing a dense in-situ network to sample the field continuously in time for all ranges of variability is impractical. However, a sparser but smarter network with an optimized measurement schedule can provide the validation estimates by operating in a guided fashion with guidance from its own sparse measurements. The feedback and control take place in the context of a dynamic physics-based hydrologic and sensor modeling system. The overall design of the smart sensor web-including the control architecture, physics-based hydrologic and sensor models, and actuation and communication hardware-is presented in this paper. We also present results illustrating sensor scheduling and estimation strategies as well as initial numerical and field demonstrations of the sensor web concept. It is shown that the coordinated operation of sensors through the control policy results in substantial savings in resource usage.IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing 01/2011; · 1.49 Impact Factor -
Article: Measurement Scheduling for Soil Moisture Sensing: From Physical Models to Optimal Control
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ABSTRACT: In this paper, we consider the problem of monitoring soil moisture evolution using a wireless network of in situ sensors. Continuously sampling moisture levels with these sensors incurs high-maintenance and energy consumption costs, which are particularly undesirable for wireless networks. Our main hypothesis is that a sparser set of measurements can meet the monitoring objectives in an energy-efficient manner. The underlying idea is that we can trade off some inaccuracy in estimating soil moisture evolution for a significant reduction in energy consumption. We investigate how to dynamically schedule the sensor measurements so as to balance this tradeoff. Unlike many prior studies on sensor scheduling that make generic assumptions on the statistics of the observed phenomenon, we obtain statistics of soil moisture evolution from a physical model. We formulate the optimal measurement scheduling and estimation problem as a partially observable Markov decision problem (POMDP). We then utilize special features of the problem to approximate the POMDP by a computationally simpler finite-state Markov decision problem (MDP). The result is a scalable, implementable technology that we have tested and validated numerically and in the field.Proceedings of the IEEE 12/2010; · 6.81 Impact Factor -
Conference Proceeding: A structural result for delayed sharing information structures
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ABSTRACT: The n-step delayed sharing information structure is investigated. This information structure is a link between the classical information structure, where information is shared perfectly among the controllers, and a non-classical information structure, where there is no “lateral” sharing of information among the controllers. A structural result for optimal control policies in systems with such information structures is presented. A methodology for sequentially finding optimal policies is also established. The solution approach provides an insight for identifying structural results for general decentralized stochastic control problems.American Control Conference (ACC), 2010; 08/2010
